It is known for containers such as boiling devices, cooking vessels, frying or roasting pans or the like, to be heated by means of a heater assembly comprising a tubular casing in which a heating coil is disposed. In order to form an end seal at the ends of the heating assembly, where it extends out of the container, a connection pin member which is connected to the heating coil in the tubular heater casing is passed through an insulating sleeve in the wall of the container and the part of the connection pin member which projects out of the insulating sleeve is provided with a plug connecting pin for connection to an electrical plug.
However in a tubular heater assembly of this kind, there is often the problem that mechanical forces acting on the plug pin, and repeated expansion and contraction phenomena in the heater assembly result in the seal becoming loose so that water can penetrate to the electrical components when the vessel is being cleaned, and can thereby impair the insulation thereof.
In addition, temperatures of up to about 250.degree. C. will often occur at the connection ends of the tubular heater, so that silicone rubber discs which are normally used for sealing purposes at those locations can no longer satisfactorily carry out their function as a result of the flow behaviour of silicone rubber at such temperatures, and subsequent hardening.
In order to ensure that no water can reach the end of the heater coil in the casing, German Auslegeschrift No. 1 128 060 discloses an end seal means which is intended to overcome the above-indicated problems. In this disclosed end seal means, an intermediate disc is provided between the end surface of the tubular casing and the inwardly facing end surface of a sleeve or bush, for example of boron silicate glass, which in turn is pressed with its edge portion against the wall of the vessel or container by way of a further interposed sealing ring, by a rearward flange portion on the plug pin fixed on the outwardly projecting part of the connection pin member of the heater assembly.
However, this construction does not take into account the fact that forces which act on the plug pin when the electrical connection cable is frequently plugged in and disconnected, can result in the connection pin member becoming loose in the insulating material, thereby reducing the pressure force applied by the sleeve to the side wall of the vessel and by the intermediate disc to the end surface of the tubular casing, and this ultimately also results in a loss of sealing action.